Crystallization of salts from aqueous solutions



Patented Aug. 28, 19e5 I I i UNITED .JSTATES PATENT orrlcs cnrs'rahuza'non on SALTS mom AQUEOUS sou -nous Baden, Bloch and Isaac Schnerb, Jerusalem, Palestine, assignors to Palestine Potash Ltd., Jerusalem, Palestine, a British company e No Drawing; Application January 21, 1943, Serial No. 473,114. In Palestine November 10, 1942 14 Claims. (01. 23-295 This invention relates to the crystallization of in the same brine: If equal portions of the same salts from their aqueous solutions by the evapobrine are coloured respectively with solid naphration of the water by means of solar radiation thol green and an equal concentrati n of th d and has as its object to increase the rate of evapstun according to this invention, the latter pororation of the water. The term evaporation as tion retains its green colour longer than the forused in connection with this invention is not mer one. a meant to imply that the solution must be evapo- The said dry mixture may directly be dissolved rated to dryness but the invention applies equally in the brine to be evaporated, provided the salt to the case that by the evaporation, the salt soconcentration of the latter is not too'hi h, Say lution is only concentrated to the desired extent. not higher th n ordinary sea .water. However. as

The invention is especially, but by no means the amount of-dyestuff required for producing the exclusively, useful in connection with the cryscorrect shade of the brine is rather small, the tallization of salts from natural brlnes, particu- 1 concentration of the reagents in the brine w uld larly from sea water, such as sodium or potasin most cases be too small to allowthereaction slum chloride, carnallite, potassium bromide and 1 w n t e o me about Therefore. t is the like. advisable to prepare separately a dyestufi 11-, s -n e been ascertained th t th evapotlon in water or a dilute brine and to add this to ration process can be accelerated by dissolving in the br n to be evaporated- 1 the brine a dyestufl absorbing the visible part of Example the solar spectrum, or at least a substantial portion thereof, the dyestufl being advantageously A dry mixture is prepared from 100 grs. of

so selected that the ultra-red rays of solar radisghfifiers alt, 32 grs, of sodium nitrite and 60 ation near the visible light are equally absorbed. grs; of ferrous. sulfate (FeSOr'ZHzO). All the We have now found thata particularly eflicient components must be dry. The mixture is a yelcolouring of salt solutions 'for the purpose in view lowish powder which, if protected against the acy be obtained by means of a dry mixture concess of moisture, keeps for a long time.- taming schfifiers Salt (that an ali r 24 grs. of this mixture are dissolved under stirm ni m S f ph -filf nic a id). an ring in 300 grs. of water, the temperature-of the a kali nitrite and an ir n salt n whi h .mixture solution being kept below C. By the reaction the Said substances are Suitably sent in a pro- 30 which starts soon, a dark brown liquor is obtained. .portion of about one mole of nitrite and half a of this liquor, about 40 ccs. are added to each mole of iron salt (in the s f -f rro mcubic meter of the brine to be evaporated wherepound, for example, ferrous sulfate) or one third by the latter assumes a bright green colour. Of

0! a mole of iron salt (in the case of a ferric comcourse, the amount of dyestuif to be added to the pound, for example, ferric chloride) for each mole brine may vary within wide limits, according to of Scht'lflers salt; he f rma i n f a dyestufi takthe concentration of the brine and climatic face ing place by the interaction of said substances on tors including the intensity of the sun radiation taking up the mixture in water or a neutral salt available, the average wind velocity and the husolution. The reaction thus occurring is, of midity of the air. The'increase of evaporation is course, the introduction into the molecule of 40 roughly proportional to the amount of dyestufi Schafiers salt of a nitrosogroup and the comadded. It is to be noted, however, that there exblnation of a number of'molecules of nitroseists a certain optimal proportion, to be deter- Schiflfer's salt with an iron atom into a complex mined according to the special circumstances of molecule, as described in our co-pending patent each case, beyond which the addition of even application Serial No. 473,113. The reaction liqlarge amounts of dyestufi entails only a relatively uor so obtained has a dark brown colour and small further increase of the rate of evaporation jtums green 011 ng it Wi Wa ei r a neutral so that the addition of dyestuff beyond this op-' salt solution, or by adding alkali until a neutral timal proportion will generally not pay. There or slightly alkaline reaction is obtained. exists, of course, an absolute limit beyond which The g een dy t fl' so produced ppears to be no amount of dyestufi can produce any further s y related to. or identical with, naphthol increase of the rate of evaporation. This limit is reen- However, it has been ascertained that given by the quantity of dyestufl sufilcient for a when admixed 0 the l 'b be e ap t d, total absorption of the impinging radiation.

the dyestuil according to this invention is defl- We claim:

ni y faster than solid naphthol reen dissolved 56 1. In the crystallization of salts from their lowing the said substances to react with one another, converting the reaction liquor into a green dyestuif solution adapted. to increase the rate of evaporation of the water from said salt solution by diluting the reaction liquor with an aqueous liquid adding said green dyestuflf solu-' tion to the aqueous solution to be evaporated and subjecting the latter to solar radiation.

2. In the crystallization of salts from their "aqueous solutions by evaporation by means of solar radiation, the steps of dissolving in an aqueous liquid a dry mixture containing Schaffers salt, an alkali nitrite and an iron salt, allowing the said substances to react with one another, converting the reaction liquor into a green dyestufi solution adapted to increase the rate of evaporation of the water from said salt solution by adding an alkaline reacting substance to said reaction liquor adding said green dyestufi solution to the aqueous solution to be evaporated and subjecting the latter to solar radiation.

5. In the crystallization of salts from their aqueous solutions by evaporation by means of solar radiation, the steps of dissolving in an aqueous liquid a dry mixture containing Schaffers salt, sodium nitrite and ferrous sulfate in a proportion of substantially one mole of sodium nitrite and half a mole of ferrous sulfate for each mole of Schaifers salt, allowing said substances to react with one another; adding the reaction liquor to .the salt solution to be evaporated to obtain a green solution, and subjecting the latter to solar radiation.

4. In the process of recovering salts from their aqueous solutions by dyeing the latter with a dyestuif absorbing at least a portion of the solar spectrum, and evaporating the solutions by means of solar radiation, the improvement which comprises dyeing said solutions by means of a product obtained by reacting a mixture containing Schafiers salt, an alkali nitrite and an iron salt in an aqueous liquid in the absence of added acid.

5. The process set forth in claim 4in which said product is treated with a substance having an alkaline reaction, and then dissolved in said solutions.

6. The process set forth in claim 4 in which said product is diluted with an aqueous liquid and then dissolved in said solutions.

'7. The process set forth in claim 4 in which the components of said mixture are present in a proportion of substantially one mol of nitrite 'and mol of ferrous salt for each mol of Schiifier's salt.

- 8. The process set forth in claim 4 in which the components of said mixture are present in aqueous solutions by evaporation by means 01' solar radiation, the steps of dissolving in an aqueous liquid a dry mixture containing Schiiffers salt, an alkali nitrite and an iron salt, allowing said substances to react with one another, converting the reaction liquor into a green dyestuif solution adapted to increase the rate of evaporation of the water from the salt solution to be evaporated, and subjecting the salt solution to be evaporated to solar radiation in the presence of said dyestufl solution.

10. In the crystallization of salts from their aqueous solutions by evaporation by means of solar radiation, the steps of dissolving in water a dry mixture containing Schiiflers salt, an alkali nitrite and an iron salt, allowing the said substances to react with one another, converting the reaction liquor into a green dyestufl' solution adapted to increase the rate of evaporation of the water from the salt solution to be evaporated, and subjecting the salt solution to be evaporated to solar radiation in the presence of said dyestuff solution.

11. In the crystallization of salts from their aqueous solutions by evaporation by means of solar radiation, the steps of dissolving in a dilute aqueous salt solution a dry mixture containing Schafier's salt, an alkali nitrite and an iron salt, allowing the said substances to react with one another, converting the reaction liquor into a green dyestufi solution adapted to increase the rate of evaporation of the water from the salt solution to be evaporated, and subjecting the salt solution to be evaporated to solar radiation in the presence of said dyestuif solution.

12. In the crystallization of salts from their aqueous solutions by evaporation by means of solar radiation, the steps of dissolving in the salt solution to be evaporated a dry mixture containing Schaffers salt, an alkali nitrite and an iron salt, allowing said substances to react with one another, converting the reaction liquor into a green dyestufl solution adapted to increase the rate of evaporation of the water from said salt solution and subjecting said salt solution to solar radiation.

13. In the crystallization of salts from their aqueous solutions by evaporation by means of solar radiation, the steps of dissolving in an aqueous liquid a dry mixture containing Schiiffers salt. an alkali nitrite and a ferrous salt in a proportion of substantially one mole of alkali nitrite and half a mole of ferrous salt for each mole of Schafiers salt, allowing the said substances to react with one another, converting the reaction liquor into a green 'dyestufi solution adapted to increase the rate of evaporation of the water from the salt solution to be evaporated, and subjecting the salt solution to be evaporated to solar radiation in the presence of said dyestufl solution.

14. In the crystallization of salts from their aqueous solutions by evaporation by means of solar radiation, the steps of dissolving in an aqueous liquid a dry mixture containing Schiiffers salt, an alkali nitrite and a ferric salt in a proportion of substantially one mole of nitrite and one-third of a mole of ferric salt for, each mole of Schaifers salt, allowing the said substances to react with one another, converting the reaction liquor into a green dyestuff solution adapted to increase the rate of evaporation of the water from the salt solution to be evaporated, and subjecting the salt solution to be evaporated to solar radiation in the presenceof said dyestufi solution.

RUDOLFBLOCH. ISAAC SCHNERB. 

